The winner will take on Tim Mahoney, the incumbent Democrat, in November. Retaking the seven-county district is considered a top priority for Republicans.

"Tom's a friend," Crist said during a stop before a crowd of GOP leaders and officials from Palm Beach and Martin counties inside Rooney's Public House in Abacoa. "I know of his skill and work ethic."

Harrell responded that Crist shouldn't be making endorsements in Republican primaries. She added the governor only did so because of influential and well-connected lobbyists with ties to both Rooney and Crist.

"I think had the endorsement been about the issues, then Charlie would be endorsing Gayle Harrell," Harrell said.

Valeche's campaign said Crist's decision and trip to Jupiter was about gambling money and shows Rooney and Crist's lack of conservative Republican principles.

"The GOP has received $4 million from gambling interests since Charlie Crist took office," Rudnick added. "That is something that would not have happened while Jeb Bush was in office."

Valeche has made opposition to gambling a big part of his campaign and Rudnick noted the Rooney family trust, which also owns the Palm Beach Kennel Club in West Palm Beach, has given $700,000 to the Republican Party of Florida in the past two years.

When asked about Valeche's claims, Crist responded, "I'm here for Tom Rooney and I want to do everything I can to help him win."

As part of the growing bitterness in the race, the Kennel Club's president, Pat Rooney Sr., the candidate's father, has threatened Valeche with a lawsuit over a newspaper editorial in which Valeche criticized the kennel club's proposal to expand gambling.

Rooney, who along with Harrell has been the target of commercials by Valeche, said the endorsement has been in the works all week and that he doesn't intend to get into a debate of issues outside the race.

"We're going to continue to talk about the issues, about why I should be a congressman," Rooney said. "You know at the end of the day that's what people want to hear about."